DESCRIPTION (provided by investigator): Converging evidence (e.g., Badian, 1983;Gross-Tsur, Manor, &Shalev, 1996) reveals that 4-7 percent of the school-age population suffers from learning disabilities in mathematics (MD). Although this prevalence rate is similar to that of reading disability, much less systematic study has been directed at MD (cf. Rasanen &Ahonen, 1995). This relative neglect is problematic because MD is a serious public health problem, leading to life-long difficulties in school and in the workplace and creating financial burdens on society. Mathematics competence, for example, accounts for variance in employment, income, and work productivity even after intelligence and reading have been explained (Rivera-Batiz, 1992). The purpose of this project is to increase understanding about and decrease the prevalence of MD. Our focus is arithmetic number combinations (sometimes referred to as arithmetic facts): addition and subtraction problems with 1-digit operands (e.g., 3+5;9-2) for which answers can be retrieved directly from long-term memory. Number combinations are a signature deficit of students with MD and are thought to be a precursor to and partial explanation for difficulties with other math skills (e.g., Fuchs et al., 2006). Research on number combination deficits has focused predominantly on describing performance differences between groups of students with and without MD. Less is known about (a) the potential to prevent difficulties with number combinations when intervention for students at risk for MD begins in 1st grade;(b) what the appropriate focus and nature of that intervention should be;(c) whether maintenance effects can be expected longitudinally;(d) whether transfer effects to other math skills can be expected in the short- and long-term;(e) the relative contribution of domain-general abilities versus a defective number module in accounting for variance in outcomes on number combinations and other math skills in the short- and long-term;and (f) how child characteristics that predict outcome differ depending on the nature of intervention. The goal of the proposed study is to address these issues and thereby improve outcomes for the MD population and increase understanding about MD. Relevance of this research to public health: Mathematics disability (MD) is a serious public health problem, with 4-7 percent of the school-age population suffering the disorder. MD leads to life-long difficulties in school and in the workplace and creates financial burdens on society, accounting for variance in employment, income, and work productivity even after intelligence and reading have been explained.